Weathered rocks have that familiar natural look, just like old wood. They look like part of the natural surroundings. In contrast, a fresh rock surface looks out of place, stands out and doesn’t look natural. That’s why road cuts look so out of place. Just take a look at the roadcuts on I-40 through Kingman. They are white and have no character. The natural hills with weathered Peach Springs Tuff look tan to buff-brown. They belong and the weathering gives them that natural look.
When rocks are exposed to the elements, they’re attacked in three ways; physical, chemical and biological. Heat and cold expand and contract the surface causing cracks to form between the minerals. These cracks allow water to seep in. When water freezes in the cracks, it pushes out, widening the cracks. Exposed to water, the minerals are attacked by oxidation and weak acids. Biochemical processes also attack, converting minerals into clay. Even lichen, that colorful yellow-green composite organism (algae and or cyanobacteria) attacks the surface of rocks.
As the minerals begin to break down, they release substances like iron and manganese oxide. The oxides coat the weathered rocks and give them a darker appearance.
Road construction crews have recognized that newly exposed rock is not visually pleasing. It’s usually a much lighter color than the weathered outcrop so the newly exposed rock stands out. To speed up the weathering of the road cuts, construction crews sometimes use a compound that...
Read Full Story: https://kdminer.com/news/2021/oct/02/luis-vegas-mohave-county-geology-weathering/
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